In the treatment of disease it becomes necessary to obtain a sample of cerebrospinal fluid and/or inject material into the spinal subarachnoid compartment. According to the previous art, after the spinal cannula had been inserted and the procedure performed, the cannula was withdrawn. Fluid inside the subarachnoid space, which is under a pressure of 0.3-1.2 PSI, would then flow through a circular opening the size of 0.397 square mm to 1.26 square mm resulting from the penetration of a needle or cannula of 22 gauge (outside diameter=0.71 mm) or 18 gauge (outside diameter=1.27 mm) respectively across a pressure gradient into the subdural or the epidural compartments and subsequently decrease the intraspinal and/or intracranial cerebrospinal fluid pressure. No apparatuses are known to have been developed to plug this fluid leak. No needles or cannulae are presently marketed which can seal the pia-arachnoid/dura mater to prevent cerebrospinal fluid transfer from the subarachnoid space into the subdural space or epidural space. A "blood patch" (20 cubic centimeters of autologous whole blood) can be performed to prevent post-lumbar headache. After a spinal tap or puncture 20 cc's of a patient's own fresh whole blood is injected by a syringe into the epidural space. The whole blood clots in 4-8 minutes and forms a "patch" to prevent cerebrospinal fluid from leaking; success is irregular and intra-spinal pressure dynamic change is difficult to check. Another method to minimize the mortality and morbidity of the spinal tap is to minimize the needle diameter size to 26 gauge 0.457 mm diameter); this small sized needle requires a pressure transducer for pressure readings and usually a pump for fluid withdrawal.
The spinal tap can cause death by cerebral herniation through the tentorial notch and/or foramen magnum. The spinal tap can also cause sudden irreversible paraplegia. The spinal tap in a series of over 500 patients increased the risk of death 1000% in patients with increased intracranial pressure without papillaedema, fatalities reaching 12% (Marton and Gean, Annals of Internal Medicine, 104:840 (1986)). Complications include: (1) headache; (2) infection; (3) nerve/spinal cord injury; (4) bleeding.
Present indications for performing a spinal puncture are the following: (1) diagnosis of bacterial meningitis; (2) diagnosis of mycobacterial and fungal meningitis; (3) diagnosis of subarachnoid hemorrhage; (4) diagnosis of neoplastic meningitis; (5) diagnosis of viral encephalitis; (6) diagnostic study of myelography; (7) diagnostic study of isotope cisternography. Therapeutic uses of the spinal tap include: (8) subarachnoid steroid injection; (9) cerebrospinal fluid removal as treatment for cerebrospinal fistula; (10) epidural analgesic instillation; (11) epidural block anesthesia; (12) palliative subarachnoid injections for interminable pain.
It is accepted axiomatically that neurological deterioration can result from shifting of intracranial parts caused by intercompartmental pressure gradients or differences. Intracranial and cervical intraspinal fluid pressures have been measured in patients with an enlarging intracranial mass, revealing grossly different pressures in these two compartments. Because of this intercompartmental gradient--high pressure intracranially and low pressure intraspinally--it is considered very dangerous to perform a spinal puncture which would increase the pressure gradient. In one series (Connley E. S., in Yoomans JR. Philadelphia: W. B. Saunders, 5:3196 1982) of 30 patients with an enlarging intracranial mass, the following developed after a lumbar puncture: (1) three--immediate apnea; (2) seven--unequal pupils; (3) twelve--death. This study showed 40% death rate with increased intracranial pressure secondary to an expanding mass.
A pressure gradient can also exist in the spinal canal: spinal tumor produces a complete spinal subarachnoid block causing an intraspinal pressure gradient, i.e., high pressure above mass and low pressure below mass. Sudden paralysis after a spinal puncture below a block can occur--the cerebrospinal fluid below the block having provided a critical buffer. When the cerebrospinal fluid was removed from the subarachnoid space by spinal tap or subsequent dural leak, the spinal cord was compressed by the pressure gradient with physiological function cessation and/or anatomical injury. This phenomenon has been termed "spinal coning" and has been given in incidence of 25%. Even if a small amount of fluid is removed below a spinal pressure gradient, fluid subsequently continues to leak from the subarachnoid compartment into subdural compartment and/or epidural compartment. This deterioration of neurological function of patients with a spinal compartment pressure gradient following a spinal tap has occurred in as short a time as 30 minutes to up to 4 days after the procedure. This later onset attests to the continued leakage of cerebrospinal fluid out of the subarachnoid space aggravating the intraspinal pressure gradient.